From: Bartosz Golaszewski bgolaszewski@baylibre.com

When allocating an array of elements, users should check for multiplication overflow or preferably use one of the provided helpers like: kmalloc_array().

There's no krealloc_array() counterpart but there are many users who use regular krealloc() to reallocate arrays. Let's provide an actual krealloc_array() implementation.

While at it: add some documentation regarding krealloc.

Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com Acked-by: Vlastimil Babka vbabka@suse.cz --- Documentation/core-api/memory-allocation.rst | 4 ++++ include/linux/slab.h | 18 ++++++++++++++++++ 2 files changed, 22 insertions(+)

diff --git a/Documentation/core-api/memory-allocation.rst b/Documentation/core-api/memory-allocation.rst index 4446a1ac36cc..6dc38b40439a 100644 --- a/Documentation/core-api/memory-allocation.rst +++ b/Documentation/core-api/memory-allocation.rst @@ -147,6 +147,10 @@ The address of a chunk allocated with `kmalloc` is aligned to at least ARCH_KMALLOC_MINALIGN bytes. For sizes which are a power of two, the alignment is also guaranteed to be at least the respective size.

+Chunks allocated with `kmalloc` can be resized with `krealloc`. Similarly +to `kmalloc_array`: a helper for resising arrays is provided in the form of +`krealloc_array`. + For large allocations you can use vmalloc() and vzalloc(), or directly request pages from the page allocator. The memory allocated by `vmalloc` and related functions is not physically contiguous. diff --git a/include/linux/slab.h b/include/linux/slab.h index dd6897f62010..be4ba5867ac5 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -592,6 +592,24 @@ static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags) return __kmalloc(bytes, flags); }

+/** + * krealloc_array - reallocate memory for an array. + * @p: pointer to the memory chunk to reallocate + * @new_n: new number of elements to alloc + * @new_size: new size of a single member of the array + * @flags: the type of memory to allocate (see kmalloc) + */ +static __must_check inline void * +krealloc_array(void *p, size_t new_n, size_t new_size, gfp_t flags) +{ + size_t bytes; + + if (unlikely(check_mul_overflow(new_n, new_size, &bytes))) + return NULL; + + return krealloc(p, bytes, flags); +} + /** * kcalloc - allocate memory for an array. The memory is set to zero. * @n: number of elements.

From: Bartosz Golaszewski bgolaszewski@baylibre.com

Use the helper that checks for overflows internally instead of manually calculating the size of the new array.

Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com Acked-by: Michael S. Tsirkin mst@redhat.com --- drivers/vhost/vringh.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 8bd8b403f087..08a0e1c842df 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -198,7 +198,8 @@ static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)

flag = (iov->max_num & VRINGH_IOV_ALLOCATED); if (flag) - new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp); + new = krealloc_array(iov->iov, new_num, + sizeof(struct iovec), gfp); else { new = kmalloc_array(new_num, sizeof(struct iovec), gfp); if (new) {

From: Bartosz Golaszewski bgolaszewski@baylibre.com

Use the helper that checks for overflows internally instead of manually calculating the size of the new array.

Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com Acked-by: Borislav Petkov bp@suse.de --- drivers/edac/ghes_edac.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c index a918ca93e4f7..6d1ddecbf0da 100644 --- a/drivers/edac/ghes_edac.c +++ b/drivers/edac/ghes_edac.c @@ -207,8 +207,8 @@ static void enumerate_dimms(const struct dmi_header *dh, void *arg) if (!hw->num_dimms || !(hw->num_dimms % 16)) { struct dimm_info *new;

- new = krealloc(hw->dimms, (hw->num_dimms + 16) * sizeof(struct dimm_info), - GFP_KERNEL); + new = krealloc_array(hw->dimms, hw->num_dimms + 16, + sizeof(struct dimm_info), GFP_KERNEL); if (!new) { WARN_ON_ONCE(1); return;

From: Bartosz Golaszewski bgolaszewski@baylibre.com

Use the helper that checks for overflows internally instead of manually calculating the size of the new array.

Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com --- drivers/hwtracing/intel_th/msu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c index 3a77551fb4fc..7d95242db900 100644 --- a/drivers/hwtracing/intel_th/msu.c +++ b/drivers/hwtracing/intel_th/msu.c @@ -2002,7 +2002,7 @@ nr_pages_store(struct device *dev, struct device_attribute *attr, }

nr_wins++; - rewin = krealloc(win, sizeof(*win) * nr_wins, GFP_KERNEL); + rewin = krealloc_array(win, nr_wins, sizeof(*win), GFP_KERNEL); if (!rewin) { kfree(win); return -ENOMEM;